Gonad transcriptome of discus fish (Symphysodon haraldi) and discovery of sex-related genes

Discus fish (Symphysodon haraldi) is a well-known and economical ornamental fish. In this study, RNA-seq technology was applied to de novo assemble a gonad transcriptome of discus fish, and to discover sex-related genes. Assembly of these reads generated 115,050 transcripts, corresponding to 97,074 non-redundant unigenes, with an average length of 748bp and N50 length of 1,531bp. A total of 14,073 unique proteins were assigned at least one Gene Ontology (GO) category and 52,764 unigenes involved in 345 predicted KEGG metabolic pathways were identified. More importantly, about 12 candidate genes involved in sex determination were identified. Furthermore, 10,571 single nucleotide polymorphisms and 26,083 simple sequence repeats were also detected. The results of the present study can provide basic information for examining the potential roles of sex-related genes in the sex determination of discus fish.